The top down, a ludicrous country tune about honky tonks on the radio and neon signs trying to lure you off the highway for a quirky pit stop - the road trip is an integral part of the American dream.

The United States is a country built for driving holidays. Easy-driving roads make stints behind the wheel pleasantly manageable, but the sheer size of the country makes epic easy to take on if desired.

Natural wonders alternate with historic sites and bewildering but entertaining oddities. It is a country that has grown up catering for road trippers - the ubiquitous motels and drive-throughs have flourished for a reason - and whichever route you choose, there are likely to be hundreds of things to see and do on the way.

Some routes are more special than others, so we have picked out six of the best for that drive of a lifetime.

ROUTE 66

Where and why? The classic road trip, from Chicago to Los Angeles is about 4000 kilometres and passes through eight states of glorious Americana. Desert scenery, roadside kitsch and small-town homeliness create a recipe for magic.

How long? Two to three weeks.

Must-sees: About three hours south-west of Chicago, Springfield was the home town of Abraham Lincoln, and it is not shy about promoting this. Lincoln's huge and somewhat phallic tomb is there, as is the Abraham Lincoln Presidential Library and Museum..

The setting for Breaking Bad, Albuquerque in New Mexico is a major hotspot for hot-air ballooning. World Balloon offers US$159 (NZ$185.6) champagne flights with views of the surrounding deserts and mountains, while the Anderson-Abruzzo International Balloon Museum contains numerous world record-breaking craft and a gripping history of the sport. See worldballoon.com and balloonmuseum.com.

It is not quite on the road itself, but the Grand Canyon is only a short detour away on the Arizona stretch. Amazing views come as standard. Hiking trails, rafting trips, mule rides down into the canyon and bike rides along the South Rim are all bonus options. See nps.gov/grca.

Something weird: Installation art does not get much weirder than the Cadillac Ranch, just outside Amarillo. With their front ends buried in the dirt of the vast Texas plain, a series of eye-poppingly spray-painted Cadillacs stand to attention like psychedelic dominos.

Special stay on the way: The Wigwam Motel, as the name suggests, allows you to live out those cowboys and Indians fantasies under a genuine wigwam for from US$65 (NZ$75.87) a night. See galerie-kokopelli.com/wigwam.

THE GREAT RIVER ROUTE

Where and why? About 3330 kilometres along the Mississippi River, from its headwaters in Minnesota to New Orleans, indulging in American music heritage.

How long? Two to three weeks, but focus on the southern section if you are time-pressed.

Must-sees: Memphis is steeped in musical heritage, and the Graceland complex acts as the grand high temple of all things Elvis. It is stunningly tacky, but that is what makes it so much fun. Where else can you see his private jet or pink Cadillac? The city's more serious side comes at the National Civil Rights Museum, inside the converted hotel where Martin Luther King jnr was assassinated in 1968. See elvis.com/graceland and civilrightsmuseum.org.

If the blues is more your cup of tea, Clarksdale in Mississippi is ground zero. It gave the world John Lee Hooker, Muddy Waters and Ike Turner, and the Delta Blues Museum tells the story. Hit the juke joints for the living thing, for the visitor-friendly Ground Zero Blues Club is co-owned by actor Morgan Freeman. See deltabluesmuseum.org and groundzerobluesclub.com.

Before throwing yourself into the bourbon-soaked mayhem of New Orleans, go back in time to the genteel old Mississippi with a cruise on a paddlewheeler. The Creole Queen offers options going past old battlefields or with jazz over dinner. See Creolequeen.com.

Something weird: Wisconsin is traditionally the home of American brewing, and the town of La Crosse plays host to the World's Largest Six Pack. Six giant tanks are painted to look like beer cans, and they could hold more than 7 million of the real things.

Special stay on the way: The Shack-Up Inn at Clarksdale's Hopson Plantation has converted sharecroppers' shacks into cool accommodation from US$70 a night. It is also a live music venue. See shackupinn.com.

THE NEW ENGLAND FALL LOOP

Where and why? Boston to Boston, via the forests, hills and coastline of New England. It is best done in autumn, when the soon-to-fall leaves change colour and make the region look like a giant kaleidoscope.

How long? Five to 10 days, depending on the route.

Must sees: The Cannon Mountain Aerial Tramway in New Hampshire offers the region's best views. It's possible to see four states plus a bit of Canada from the top of the mountain. See cannonmt.com.

In Maine's mountains and Western Lakes region, autumn is moose-breeding season, and that tends to mean the big beasts are easier to spot in the wild.

The region was where the American Revolution began, and key sites are dotted throughout. For the best overview, try the Minute Man National Historical Park. It offers a good combination of multimedia presentations, re-enactments, battlefield walking trails and old colonial era houses to explore.nps.gov/mima.

Something weird: It is permanently Hallowe'en in Salem, the Massachusetts town notorious for its witch trials. The ghost tours, witch-themed attractions and horror film museums are so over the top, they are thoroughly enjoyable. See Salem.org.

Special stay on the way: Sound of Music fans will be unable to resist the faux-alpine kitschfest of the Trapp Family Lodge. When Maria and the rest of the von Trapp family fled from Austria, this is where they ended up, and the lodge is still run by the family, offering doubles from US$260. See trappfamily.com.

THE BLUE RIDGE PARKWAY

Where and why? Stretching 755 kilometres from the Great Smoky Mountains National Park, North Carolina, to the Shenandoah National Park, Virginia, this mountain-hugging route is mostly flanked by national park, and can be done as part of a larger Atlanta to Washington, DC, route.

How long? Up to a week for the short version and up to two weeks for the full Atlanta to Washington stretch.

Must-sees: The Blue Ridge Parkway is about swapping driving gloves for hiking boots. The 12-kilometre Bluff Mountain Trail in Doughton Park, North Carolina, is full of dicey switchbacks and sweeping views.

Grand Caverns in Virginia is the US's oldest show cave complex. What makes it unusual is the mix of the predictable natural formations, such as stalagmites and stalactites, and history. The caverns became a shelter for both sides in the American Civil War, and many soldiers signed their names on the walls. See Grandcaverns.com.

In northern Virginia, Mount Vernon was the plantation home of the first US president, George Washington. The museum gives fascinating insights into the man and era, and the slave quarters may cause you to reassess his reputation for greatness. See Mountvernon.org.

Something weird: A short detour over the Tennessee border brings you to unquestionably the world's greatest Dolly Parton-themed amusement park. See Dollywood.com.

Special stay on the way: The Mountain Lake Lodge in Virginia offers its own zipline course, and doubles from $US110. It also had a starring role in the movie Dirty Dancing. See mtnlakelodge.com.

THE PACIFIC COAST HIGHWAY

Where and why? From Los Angeles to San Francisco along the Californian Coast, this is all about curving clifftop roads, the wild forest-backed beaches of Big Sur and surprising amounts of wildlife on the way.

Hearst Castle is what happens when you throw unlimited funds at your house. Billionaire publishing magnate William Randolph Hearst had his 165-room home kitted out with mediaeval furniture and Roman antiquities. The tours around the grounds and rooms are predictably gob-smacking, but the biographical insights into the parties Hearst hosted are just as astonishing. See hearstcastle.org.

An undersea canyon runs beneath Monterey Bay, which makes it an aquatic wildlife hotspot. It is a playground for humpback whales, orcas, seals and sea otters. Sanctuary Cruises at Moss Landing runs longer trips on smaller boats than its competitors, and has a marine biologist on board. They cost US$50. See sanctuarycruises.com.

Something weird: Good luck trying to get towel space on the Piedras Blancas beach, just north of Hearst Castle. It has been taken over by honking, scrapping and wonderfully watchable elephant seals. See elephantseal.org.

Special stay on the way: The Inn at Spanish Bay backs on to Pebble Beach, one of the world's most famous golf courses, but the sunsets from the private patios are worth putting the clubs down for, even at US$745 a night. See pebblebeach.com.

THE OVERSEAS HIGHWAY

Where and why? About 260 kilometres from Miami to Key West, via the Florida Keys and over a large number of bridges that stretch for miles over clear blue sea. This may be the baby-steps version of the great US road trip, but it will long remain in the memory.

How long? A couple of days to a week (return).

Must-sees: The southern tip of Florida is dominated by the sticky swamplands of the Everglades, technically the world's slowest moving river.

It is possible to head out on an airboat with a giant fan at the back, trying to spot alligators on the waterways. If they are being reticent, never fear - there are alligator and snake shows back at base. See everglades.com.

There is some fine diving and snorkelling to be done around the Keys - the chain of small islands dotting out from the mainland. The Key Largo National Marine Sanctuary has arguably the best underwater eye candy, including the submerged bronze Christ of the Abyss statue. Keys Diver runs separate daily snorkelling and diving trips for from US$36.95). See keysdiver.com.

Key West, at the end of the road, lets it all hang loose and the person next to you at the bar mainlining margaritas could be a derelict, a Hollywood star or a chief executive. It doesn't really matter. Everyone's equal.

Amid the shambling around half cut on frozen daiquiris, sights include author Ernest Hemingway's old home, which is now overrun by six-toed cats. See hemingwayhome.com.

Something weird: The Coral Castle south of Miami is a head-scratching puzzle, mainly because no one knows how reclusive Latvian creator Edward Leedskalnin managed to build and hand-carve everything without help. See coralcastle.com.

Special stay on the way: You are driving over water, so you may as well stay on the water too. The Floating Inn at Key Largo offers blissed-out house boat accommodation from US$75 a night.

After picking the route and booking the flights, you'll need a car. Unless you're hankering after something specialist, comparison sites such as CarRentals.com and VroomVroomVroom.com.au are the best places to start the search. Use filters if you want to home in on 4WDs, SUVs or convertibles - otherwise use specialist sites such as blacktopcandys.com for Mustangs and CruiseAmerica.com for campervans.

There are exceptions (such as within the California-Las Vegas-Phoenix triangle or between the major east coast cities), but most routes will attract a largely unavoidable one-way fee. This is usually US$300 ($350) for distances of more than 480 kilometres and $500 for distances of more than 800 kilometres.

Also be aware that the standard insurance included by law covers you for virtually nothing - it's worth taking out excess insurance with the likes of Tripcover.com.au from $10.38 a day.

When planning your route, try the individual state tourist board sites and those concentrating on particular routes, for example, Pacific-coast-highway-travel.com. Roadtripusa.com and Roadtripamerica.com do a good job of covering US driving holidays as a whole. Google Maps (maps.google.com) is very useful for working out approximate driving times between stops.

For accommodation, roadside motels generally have better standards than their reputations suggest. The perfectly passable likes of Super 8s (super8.com) and La Quintas (lq.com) start at about $60, but prices vary massively by location.